This invention relates to supplementary fuel supply device, which can be incorporated into a carburetor, to promote starting efficiency of, for example, a two-cycle engine used as a power source for chain saws or lawn mowers. A standard carburetor mounted on an internal combustion engine has a fuel supply device built in therewith in order to supply proper amounts of fuel to said engine in accordance with its operating condition. However, in cold weather or in other conditions, the amount of fuel supplied from only said fuel supply device presents a problem in engine starting efficiency.
It has been previously suggested to provide a cavity opening in said air intake passage between the carburetor and the air intake orifice of the internal combustion engine to retain a sufficient amount of supplementary fuel necessary for engine starting. In this system, as the engine is about to start, the retained fuel in the cavity simultaneously flows into the engine because of the suction in the air supply passage and this increases the fuel mixture strength for the starting of the engine.
However, in order to maintain smooth idling of the engine immediately after its starting, it is desirable to keep supplying high mixture concentration to the engine continuously even after the starting. To satisfy this demand, it is conceivable that said cavity should be designed with a sufficient capacity to be able to hold a proper amount of supplementary fuel in the cavity for the idling run.
However, the fact that the fuel cavity is open to the air intake passage makes it possible that a large amount of supplementary fuel in the cavity may prevent the starting of the engine because of improper atomization of the supplementary fuel in the cavity flowing into the air intake passage. This may occur as a result of a slight vibration at the starting of the engine or from the tilt attitude of the carburetor, and it is feared that engine starting could be hampered because of flow of the supplementary fuel in liquid form into the engine.
In view of the foregoing, it is a general object of this invention to provide a supplementary fuel supply device that will not interfere with the engine starting, and yet retains sufficient amount of supplemetary fuel to supply the quantity needed for said engine starting and a sufficient supply for the subsequent idling run in quantities which can be satisfactorily handled by the engine.
The features of this invention are as follows: to provide a supplementary fuel retainer chamber independently of the air intake passage that connects to the air inlet through the carburetor; to provide a piloting means in said retainer chamber for piloting the retained fuel in said retainer chamber into said air intake passage; and to provide an air vent in the retainer chamber for supplying supplementary fuel of said retainer chamber into said air intake passage by suction of said air intake passage. With the foregoing method, supplementary fuel will not flow in objectionable quantities into the air intake passage either as a result of vibration or slight tilt attitude, and yet a sufficient amount of supplementary fuel can be provided for the idling stage of the engine.
Other features of the invention will be apparent in the following description and claims in which the invention is described, together with details to enable one skilled in the art to practice the invention.